Identification of some volatile descriptors of the rock-rose-like aroma of fortified red wines from douro demarcated region.

2,2,6-Trimethylcyclohexanone and ethyl dihydrocinnamate, known sensorial descriptors of rock-rose (Cistus ladaniferus) aroma, are reported as minor constituents of young fortified wines from the Douro Demarcated region (vintage 1997) for the first time. These compounds were respectively identified by GC-MS in two different fractions (A and B) obtained by preparative GC. Quantitative analysis by GC-MS was performed on 14 fortified wines originating from the different Douro subregions. Ethyl dihydrocinnamate was found to be present at concentrations between 2.3 and 6.7 microgram/L, while 2,2,6-trimethylcyclohexanone ranged from 0.05 to 0.4 microgram/L.

Chemicals with sweet aroma descriptors found in Portuguese wines from the Douro region: 2,6,6-trimethylcyclohex-2-ene-1,4-dione and diacetyl.

2,6,6-Trimethylcyclohex-2-ene-1,4-dione (TMCHD), a norisoprenoid with a sweet honey aroma descriptor, is reported for the first time as a minor constituent of single-varietal table and fortified wines from the demarcated Douro region. Olfactory gas chromatography (GC-O) of a volatile wine extract, previously isolated by preparative gas chromatography, indicated the presence of a zone containing an intense honey descriptor. The targeted odor compound was identified by GC-MS, GC-O, and Kovats index. Quantitative analysis using a selected characteristic ion (m/z 96) indicated that young Douro fortified wines from the 1997 vintage contained up to 4 microg/L TMCHD. The sweet honey sensory threshold limit for TMCHD in a model Port wine solution was found to be 25 microg/L. TMCHD is therefore only likely to contribute as a collective element to Port wine aroma. The wine volatile diacetyl was identified as a strong contributor to the sweet caramel aroma descriptor often associated with Port.